Gradometer



Sept 8, 1925.

GRADOMETEIR C. W.'GIRVIN Filed Aug. 16. 1925 Patented sept. 8, 1925 7 Ii I i V UNITED STATES PATEN OFFICE CIARLES elm-Ni i T E Put-K,CALIFORINIA. I l v 8 v i I GRA OMETE'RQ Applicant filed August 2 Serial7N0- 57,66 1.

To all whom it may concern: Figure 4 is a view ofthe type of Fig.1 1,-

Be it known thatI, CHARLES WV; GInvrN, the parts being in the positionsassumed I a citizen of the vUnited States, residing at when the vehicleis traveling on a downward Buena Park, in the county of Orange and gradeof acertain angle. i c v 5 State of California, have invented certainFigure 5 is a perspective fviewshow'ing a new and useful Improvements inGradomeportion of the operating mechanism.

ters, of which the following is a specifica- Figure 6 is aside elevationof parts shown tion, reference being'had therein to the ac- Fig; 5, thesame presenting a slightly 6O companying drawings. V a modified form} Yf V 1 This invention relates to improvements in As in devices, of thisgeneral, type, the

gradient meters, pertaining more p-articupresent invention isdesigned-to setup the .larly todevices designed to indicate thevaconditions of relative lmovement. between ,riations in grades, etc.,automatically; 7 two coacting parts of the mechanism,one of I Theinvention may be employed in various these parts being practically heldconstant lines of service, asfor instance, in subma relative to ahorizontal plane, the other part 7 rines, in motor vehicles, or inairplanes, shifting relative thereto in such manner as these uses beingto ascertain the variation .to indicate, in some form .or another, thefrom a normal horizontal plane, but,-for;tl1e angular relation of theline thatirepresents purposes of illustration, the device is showntheroad over which the vehicle is travelling 20 as employed inconnection with a motor vebearstosuch horizontal plane.

hicle, to indicate the grade over which the In the present. inventionthe maintenance vehicle may be travelling. v s of the conditions of thehorizontal plane is The objects of the invention are to .prodependentupon a suitable liquid, preferably vide a device of this generalcharacter which mercury, the specific gravity of this liquid 25 issimple and efficient in operation, durable aiding in securingefliciency,}altho-ugh other in construction, readily installed, andwhichliquids may be used to provide forservicecan be manufactured at arelativelylow cost; a able results. .The shiftable part is carried Inaddition, the'object is to provide a'dein a fixed position by some partof the vevice that is accurate in itsindications, and hielewhich changesits angle. as the vehicle 30 which is sufiiciently sensitive to changesin follows the contour variation of the road.

conditions and responsiveito such changes The device itself, in theparticular. em-

as will provide for efliciency in use, and at bodiment' shown in thedrawings, is in. the

the same time prevent temporary and ab- 7. form of a cylindrical casing10, having its normal conditions from materially affecting axisextending in a horizontal direction and th general tio I transversetothedirection of travel of'the To these and other ends, the nature ofvehicle, the casing carrying a wall 11 of ma which will be readilyunderstood, the inventerially smaller external diameter than the tionconsists in the improved construction I, internal wall of the casing,and concentric and combination of parts hereinafter more therewith, thetwowalls thus forming an an- 40 particularly described, illustrated inthe aclnular chamber 12, the axial length-of the companying drawings,and particularly cylinder being as desired, being sufli'cient pointedout in the appended claims. to permit of the carrying of a suflicient Inthe accompanying drawings,'in which amount ofmercuryv within suchchamber as similar reference characters indicate cone to provideforeflicient operation, the mer-- 45 sponding parts in the several viewscury, beingindicated at 13. r

c Figure 1' is a vertical sectional view taken The two concentric wallsare connected by through the device, theparts being shown 'a partition 1L, which may, if desired, be in position when the vehicle is travelinginformed integral with either Jor bothv walls, a truly horizontal plane.this partition extending throughout the 50 Figure'Q is a top plan view,partly in sece axial length ofthechamber and preferably tion, ofthesame. I extends radially. It is preferred that this Figure 3 is afaceview of thesame. partition be positioned-within the chamber in suchmanner that when the device as a whole is indicating that the vehicle istravelling on a truly horizontal plane, the partition will extend in atruly vertical plane. This is not actually essential, however, and maybe varied, if desired, the purpose being to divide the mercury into twob0d1es the partition being at the bottom of the chamber-and then connectthese mercury bodies by a small port 1 1 in the partition, the portbeing adjacent the bottom of the chamber. The two mercury bodies arethus in direct communication through the port,

and transference of mercury from one side to the other of the partitioncan and will take place as the instrument is being used.

Casing 10 mayhave its ends formed in any suitable manner, on form beingthat of having one end integral with the casmg cylindrical wall, theopposite end .being closed by a cap threaded to the casing; this form isshown in the drawing, the cap being indicated at 10 Other ways ofproducing a closed chamber 12 may be employed, the arrangement beingsuch that the partition will properly fit the end walls-or possiblyformed integral withone or bothso that transferenc of mercury around theends of the partition is practically prevented.

The opposing end walls carry suitcble bearings for a shaft 15 whichextends in the axis of theconcentric walls of the chamber, one of theends of the shaft, indicated at 15 extending beyond the end wall .toreceive an arm 16, presently referred to. The other end of the shaft maybe stepped in or extend through the opposite end wall,

as may be desired.

The portion of shaft 15 located between the end walls is provided withan upwardly extending arm 17 which forms art of a frame 17 formed of thearm 1'7 projecting normal to the direction of length of arm 17 andhaving its ends 17 extending clownwardly, preferably parallel to arm 17but spaced therefrom a distance suflicient to pen mit the free ends of"the arms 17 to be located approximately midway of the distance betweenthe circular walls of the chamber. Arms 17 carry floats 18, of suitableformation, arms 17 being of the same length so that the Jfloats, whenarm 17 is in a truly vertical .position, will lie in a horizontal plane.Arm 17 extends upwardly from shaft 15, and has a length such as tolocate arm 17 wholly within .the chamber, wall 11 having an opening 11to permit the passage of arm 1F, and of an angular length sufficient tocover the angular distancesth'at may be included within the .meteringlimits of the device. 1

Since the surfaceofjthe mercury normally remains on a horizontal plane,it will be readily understood that 'floats 18, when resting on thatsurface, will retain arm 17* in the vertical plane when the mercury isin equilibrium, even though the casing 10 should be shifted rotativelyon its axis. If the shift of the casing be gradual and at low speed, themercury will remain in practical equilibrium due to the transference ofmercury through .port 14-it being understood that shifting of the casingwill shift the position of partition 14. Where the shifting of thecasing is sudden or with rapidity, there may be a small tendency to lagin responsiveness, since the amount of mercury transferrable per unit oftime is limited by the size of the port 1 1 Under these latterconditions, the surface of the mercury in the chamber on opposite sidesof partition 14 will momentarily vary from the single horizontal plane,due to the pushing action of the partition on one of the bodies toelevate its surface and the lowering of the surface of the other bodydue to the increase in space available at the bottom to receive themercury of the body; but equilibrium is quickly restored by the transferof mercury from the high surface side of the mercury through port 14. Asthe surface of the mercury changes the position of arm 17 will changecorrespondingly due tothe action of the floats.

Owing to the possibility of a splashing of the mercury, wall 11 may havea port 11 leading to the chamber at one side of partition 14, this portpermitting escape of any mercury that may .pass throughopening 11 Aswill be understood, splashing confined to shifting mercury within thechamber provides no material damage, since it simply returns to the bodyof mercury. In this respect, the curvature of the walls is of advantagein that any abnormal splashing ef fect would tend to throw the mercurydrops inward away from the floats and on to the wall 11. A greateradvantage however, in

the concentric cylindrical wall formation is e found in the fact thatwhile the walls may move relative to the floats, the latter alwaysmaintain the same relative position with respect to the walls, due tothe fact that the walls have their movement on the same axis as th frame17, and being concentric with such axis the floats will have the samespac ing relative to the walls regardless of the position of the casingin its rotative movement.

As will be understood the casing'lO, wall 11 and partition 1 1 move inunison relative to shaft 15 and the parts carried by the lat ter. Tosupport the casing to permit this result to be obtained any suitablesupport which will hold the casing rigid with the part of the vehicle onwhich the device isv mounted, is employed. A simple arrange ment shown'in the drawing is thataof a bracket '19 connecting cap 10* with "a partllii of theindicatorportion of the device, and a pair of brackets 19""connecting the op-posite end wall of the casing to such part, thuspermanently fixing the relation between the indicator part and thecasing. Brackets 19 are spaced from the casing end Wall adistancesufficient'to permit the location of arm 16 within such spaceand outside of the casing; V

Arm. 16 carries, at its outer orfree end, a segmental rack 20, the teethof which are adapted to engage a pinion of the indicating mechanismwhich will now be described. In the embodiment of the drawing, .21

indicates the part to which brackets 19 and- 19? are secured, this partbeing that shown as the dial plate of the indicator. This plate 21 iscarried by a suitable casing 22, which may, desiredfhave an annularflange 22* by which the device can be secured on theinstrument board,(not shown) 'ofa motor vehicle, the board having an opening of properdimensions to permit the passage of the casing, etc, therethrougln sothat thelatterwillextend forward .of' the flange 22*, obviously, theconditions may be reversed so thatthe casing may extend'rean wardlyinstead of forwardly, the essential being that the generahdirection oflength of arm 16 shall extend in the direction of general movement ofthe vehicle, a direction that'is generally that of front to rear of thevehicle itself. Where the face of the instrument board is truly normalto the surface on which thevehicle is travelling, plate 21 can besecured within casing 22 in the siinple manner shown in Fig. 1; wherethe face of the instrumentboard is inclined, flange22 may befarranged tocompensate, or any other suitable arrangement employed so as to arrangeplate 21 normal to'a horizontal'plane, asinQFir 1. I-IoWever, it will 0be understood that. plate 21 need not, in service, beInoi'mal to suchhorizontal plane, Fig. ft indicating the positions of parts when saidplate is out of the position normal to the horizontal plane. Fig. 4' isintended primarily to represent the position of the device of Fig. 1when the-vehicle is traveling down grade, theindicating mechanismindicating the angle of variance from the horizontal of Figure 1;obviously, the in- ,dicating inechanismunay'be set so that'in theposition of Fig. l, the indicator may be at the neutralor horizontalplane indicating point. This is referred to simply to indicate that thedevice can be readily placed. in position for proper indicating withoutspecial preparation offparts,;if necessary or desirable. v 1 I Assumingthe. the v m'ou nting of the indicator mechanism is as in Fig.1,-with-the supporting face of the boardnormal to the vertical, the axisof plate 21 is practically in the horizontal plane'of the axis of shaft15,and the indications are provided by the movement of a pointer 23,overa calibrated scale 24 shown as carried by plate 21.

Pointer 23 is carried by a shaft 25extend ingv in the axis of plate 21,and supported by a bracket 26 carried'by the plate and by the plateitself. pinion 27 mountedbetween the bracket and Shaft 25 carries a,

plate and in position to mesh with the teeth of they segment rack 20. Asshown in Fig. 3, the pointer is in the neutral position, this being theposition of Fig. 1] under the as sumed conditions. Obviously, if theposition of the pinion be changed to the position Of'Flg. twhile thepointerfremains as iii'Fig/3, or the pointer be shifted on shaft 25,thejposition of Fig. 4 may become the neutralposition of the instrument.

It will be readily understood thatif the flange 22% of Fig. lrbe shiftedto an inclined position, the line which would "extend through shaft 25and the axis of shaft 15 would shift correspondingly, such line beingnormal to the plane of plate21. This will be understood froni Fig. 4inwhich flange 22? is shown in, such inclined position. Diir' ingthechangein position, it. willbejun'derstood that the casing 10. will also' haveshifted somewha'tindicated by the change in'position of partitionl lrelative to-a vci tical plane. As the shifting takes place, the movementof the partition has tended to change the surface 'levelof the mercuryon the opposite sides of the partition, thus shifting floats 18androcking shaft 15, so

that the initial tendency of the segment 16 wouldfbe to maintain itsrelation to the pinion as shown in Fig. l.

However, this disturbance of the normal equilibrium of the mercuryproduces the transfer of mercury through portl l to again bring thesurfaces of the mercury bodies to the same level, and this movement ofthe surfaces causes movements of the floats 18 to return frame 17tothe'position of Fig. 1, this movement of the frame being effective onshaft 15 and hence on arm 16 to shift the position of the segment rack20. This shift- 'ing of the segment-rotates pinion 27 and pointer willmove in the opposite direction.

The responsiveness of the instrument thus far described, will dependupon the size of port 149.", Should theport be sufiiciently large topermit instant response, the sensit-iveness of the instrument will besuch'as to make it diflicult'to gain an accurate reading of the scale,since any slight or short variationas for instance the striking of astone or the running into a road depression, would cause correspondingmovement of the pointer. I prefer, therefore, to employ a comparativelysmall port 14?; this will permit a fairly close response, and at thesame time tend to prevent unsteadiness of the pointer in travelling overrough roads.

In the drawings, I have shown a weight portion 28 on one of the arms 17for the purpose of acting as a counterbalance to the arm 16 and rack 20.

The structure so far described provides for efficient service andproduces accurate readings, and for general usage is satisfactory.However, there are certain conditions of service that tend to set up afalse indication, this being true in meters of this type generally; theconditions referred to are those of acceleration and deceleration of thevehicle. With either condition, the factor of the inertia of the mercuryin the chambers becomes active.

For instance, if the device be mounted in .the car as in Fig. 1 with thecasing in ad vance of the indicator, and the car traveling toward theleft, acceleration of the vehicle moves the instrument forward at acorresponding increase of speed, but there is a momentary tendency ofthe mercury bodies to lag; since the position of the partition is notchanged there is some transfer of mercury, from one side of thepartition to the other, causing a difference in level, the result beingthat there is a tendency to shift the position of the floats and thusset up motion of arm 16 to actuate the pointer; should the driver scanthe indicator at this moment he may be given a false indication. Asimilar condition exists during deceleration.

The action is due to the mobility of the mercury as compared with thatof the easing, it being necessary for the mercury to overcome theconditions of inertia before the surface is restored. The conditionrapidly vchanges to the normal, but during the period the indicationmade is more or less false, due to the fact that the disturbance of thesurfaces has affected the positions of the floats 18.

To overcome this tendency, I preferably employ a body, such as a weight,for in stance, also subject to the conditions of in ertia and which ispositioned to be active in opposition to the conditions of inertia ofthe mercury. For instance, in Fig. 5, I have shown an arm 30 extendingvertically from shaft 15, the upper end of the arm carrying a weight 31.Since shaft 15 is capable of rotating, it will be understood-that weight31is subject to the laws of inertia, and since theldirection of lag ofthe weight is:the-. sa'me as that of the mercury, and the weight and themercury are located on opposite sides of shaft 15, it will be understoodthat the movement of the floats necessary to shift arm 16 must firstovercome the resistance of weight 31. As a result, the opposing forcestend to neutralize the effect of each to shift arm 16, so that thelatter is less likely to shift position during this period. When thechange is in the direction of .deceleration, the reverse action takesplace and again the arm 16 is held in a more or less stable position. Aswill be understood the action is temporary, and hence the mercuryquickly returns to normal position.

Instead of employing a separate arm or weight, it will be understoodthat the same action can be provided by placing the proper weight 31 onframe 17, as indicated, for instance, in Fig. 6.

In either case it will be understood that when the surface of themercury is on the single plane, the weight 31 is in a state of balanceand ready for action when needed whether for acceleration ordeceleration con- .ditions.

While the movement of frame 17 in presence of a change in grade willtend to shift arm and move weight 31 in the direction which wouldseemingly tend .to increase the amount of movement of frame 17 to set upa false indication, the weight has a different action, as will beunderstood from the following:

Assuming the vehicle to be travelling toward the left in Fig. 1, and asudden change in grade equal to that shown in Fig. 4 is .encountered,the initial tendency would be to raise the float on the right throughthe rise in the level of the mercury, and to lower the float on theleft, the level of its supporting mercury being lowered; this actionwould swing the weight 31 toward the left to add its value towardtilting the frame still farther. When this action is present, the addedweight would tend to cause the float at the left to submerge to agreater extent than normal, at the same time tending to decrease theamount of submergence of the float at the right. Obviously, an increaseof submergenceof the float at the left would act to displace mercury andthus increase the depth of submergence.

Under these conditions the variation thus provided in the buoyancy ofthe two floats produces a power factor active on the float at the leftto raise the latter, this being continued by the mercury beingtransferred through port 1?, the result being that the The moment effectof weight 31 is of greatest value when its distance from its balancingpoint is greatest, and it is at this point that the maximum buoyancyvalue is present; as the:

' I shaft 15, so that thefloats are practically intheir normalconditions of-submergence.

value of the buoyancy factor decreases the moment effect also decreasessince the weight is returning toward its position of equilibrium. As themercury is approaching its position of equilibrium the weight isapproacningits vertical position where the weight is being exertedmainly on the From this it will be understood that the buoyancy factorinherently opposes the weight factor in the attempt to set up falseindications. But the presence of the weight tends to dampen the actionof, the device 5 tra'lize minor tendencies to change, without,

however, disturbing the accuracy of the meter. \Vith the weight present,port 1 F may be comparatively small.

' To balance frame 17 I preferably placea weight 28 on the arm 17opposite the direction of extension of arm 16, the weightcounterbalancing the arm andsegment.

As shown-in Fig. 3, I prefer to calibrate the indicating face insuchmanner as to indicate the-grade on each side of the neutral. I employthe usualbezel glass to protect the pointer and indication face.

Obviously, the calibrations can be et trolled as to distance in variousways, as by changing the size of the pinion, by varying the length ofarm 16, or both. 7

From the above description it is believed that the advantages will bemore or less obvious. The mercury is within a closed chamber but underno restraint as to splashing effects, the latter not affecting theoper-' ations of the device. The wall of the chamber 12 is concentricwith the axisofthe shaft 15 and is cylindrical in shape so thatregardless of the position of the instrument, the level of fluid in thechamber will remain the same. The device is simple and efficient inoperation and is of a'constr'uction that will withstand the conditionsof service.

I prefer to arrange the dimensions such that the level of the mercury isnormally somewhat below the axis of shaft 15, thus tending to preventleakage of mercury through the bearings, which can, if desired, becomparatively loose, thus decreasing the cost of manufacture.

While I have herein shown one or more ways in which the invention may bepro ice, and I therefore desire to be understood as reserving the rightto make any and all such changes or modificatlons as may be founddesirable or necessary, in so far as the same may fall within the spirtand scope of the invention asv expressed in the accompanying claims whenbroadly construed.

. Havingthus described my invention, what I-claim as new is:

:1. In grade meters and thelike, a cylindrical casing havinganannularchamber of uniform cross-section on radii of the casing,"a'perforated member extending substantially radially of the, chamber todivide the" chamber below the axis of the chamber, said chambercarryingaliquidon opposite sides of and in communication through the perforatedmember, a rigid frame pivotally mounted in such axis, floats carried bythe frame and located within said chamber on opposite sides of suchmember, indicating mechanism" including a movable indicator, and means'operatively connecting the frame and said indicator for translatingrelative movements of frame and casing into move- I ment of theindicating mechanism.

2. In grade meters and the like, a casing having an annular chamber. ofuniform' cross-section on radiiof the casing, the

chamber walls including inner and outer concentric walls spacedfro'm'thej axis of the chamber, a perforated member connecting saidwalls below such axis to divide the lower portion of said chamber, saidchamber carrying a liquid on opposite sides of and incommunicationthrough the perforations of such member, a rigid frame pivotallymounted. in such axis, floats carried by said frame and located withinsaid chamber on opposite sides of such member, indicating mechanismincluding a movable indicator, and means operatively connecting theframe and said indicator for translating relative movements of frame andcasing into movement of the indicating mechanism.

f 8. A meter as in claim 2 characterized in that the frame extendsthrough the. innerv ,wall of the chamber, vsaid wall having an upwardlyfrom the axis ofthe chamber and an arm carried thereby and extendingtransversely thereof, said latter arm carrying members extendingdownwardly within the chamber substantially parallel with the upstandingarm, each of such members carrying a float.

5. A meter as in claim 1 characterized in that the rigid frame membercarries an arm rigid therewith and outside the casing, said armextending in the direction of the indicating mechanism and carrying agear element co-operative with a companion gear element ofthe indicatingmechanism to 0peratively connect the frame with the indicator. p Y

6. A meter as in clannl characterized in that the frame includes a pivotportion which projects beyond the casing and carries an arm rigidtherewith extending in the direction of the indicating mechanism andforming a part of the means operatively connecting the frame andindicator, a counterpoise carried by the frame within the chamber forbalancing said arm.

7. In grade meters and the like, wherein variation in levels of liquidsurfaces is operative to produce movements of an indicator, a casing forthe liquid, a rigid frame pivoted in the casing floats carried by thecasing adapted to be supported by the liquid to provide relativemovement between frame and easing during variations in level of theliquid surfaces, means o-peratively connecting the frame and indicator,and means operatively connected with the frame for opposing floatmovement tending to be caused by inertia of the liquid.

8. In grade meters and the like, wherein variation in levels of liquidsurfaces is operative to produce movements of an indicator, a casing forthe liquid, a rigid frame pivoted in the casing, floats carried by thecasing adapted to be supported by the liquid to produce relativemovement between frame and casing during variations in level of theliquid surfaces, means operatively connecting the frame and indicator,and a weight element carried by the frame above the axis of framemovement and operative to oppose float movement tending to be caused byinertia of the liquid.

9. A meter as in claim 1 characterized in that the frame carries meansoperative to oppose float movement tending to be caused by inertia ofthe liquid within the chamber.

10. In a grade meter and the like, a casing, a body of liquid therein, arigid frame pivotally mounted in the casing and having depending armsequidistant from and on opposite sides of the pivot axis of said frame,floats carried by said arms respectively so as to be buoyed by saidliquid, an indicator, means operatively connecting the frame andindicator, and means carried by the frame adapted to oppose movementthereof tending to be caused by inertia of said liquid upon accelerationor deceleration of said meter. v

In testimony whereof I affix my signature.

CHAS. W. GIRVIN.

